Do Graduated Compression Garments Enhance Whole‐body Heat Loss During an Extreme Heat Exposure in Older Adults?

Abstract

Graduated compression garments worn on the lower limbs are commonly used in clinical settings to enhance blood circulation and have been shown to elicit elevations in whole‐body heat loss relative to a control condition (no compression) in young men during post‐exercise recovery in the heat (Am J Physiol 2010;299:R119). To date, it remains unknown whether these garments can enhance heat dissipation in heat vulnerable older adults. Relative to their younger counterparts, older adults demonstrate an impaired ability to increase whole‐body heat loss during an extreme heat exposure. Consequently, these individuals store more heat, leading to potentially dangerous increases in body temperature (Temperature (Austin) 2017;4:79). The use of compression garments may help alleviate the level of thermal strain in these individuals. We therefore sought to determine whether lower limb graduated compression garments would enhance whole‐body heat dissipation and reduce body heat storage relative to a control condition (i.e., no compression) in older adults during passive heat exposure. To evaluate this possibility, we assessed changes in whole‐body heat exchange and heat storage in 6 older (mean ± SD: 69 ± 6 years) adults (4 men, 2 women) during a 2‐hour extreme heat exposure (40°C, ~10 %RH) on two separate occasions (separated by ≥48 h). In both trials, participants sat in a semi‐recumbent position wearing a graduated compression garment (SCD Express Sleeves; Kendall, Mansfield, MA) on each leg containing three bladders that either delivered intermittent graded compression (ankle: 45 mmHg, calf: 40 mmHg, thigh: 30 mmHg; Compression trial) or no compression (Control trial) throughout each exposure. Trials were administered in a balanced order. Wholebody heat loss and metabolic heat production were measured continuously by direct and indirect calorimetry, respectively. Body heat storage was quantified as the temporal summation of heat production and loss. Metabolic heat production (Compression: 98 ± 10 W vs. Control: 94 ± 13 W), evaporative heat loss (135 ± 20 W vs. 134 ± 23 W), dry heat exchange (−48 ± 19 W vs. −52 ± 12 W), and net (total) heat loss (89 ± 14 W vs. 82 ± 14 W), were similar between the Compression and Control trials (all P>0.05). Consequently, cumulative body heat storage did not differ between conditions (Compression: 85 ± 11 kJ; Control: 85 ± 24 kJ, P=0.98). Our preliminary findings suggest that graduated compression garments do not enhance whole‐body heat loss in older adults during exposure to hot ambient conditions.Support or Funding InformationThe Canadian Institutes of Health Research (funds held by Dr. Glen Kenny).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.